1. Field of the Invention
The present invention relates to an imaging device and a focusing control method.
2. Description of the Related Art
In recent years, according to the increase in resolution of an imaging element such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor, demand for electronic apparatuses having an imaging function, such as a digital still camera, a digital video camera, or a mobile phone such as a smart phone, has rapidly increased. Such an electronic apparatus having an imaging function is referred to as an imaging device.
In such an imaging device, as a focusing control method for focusing on a main subject, a phase difference auto-focus (AF) method (for example, see JP2013-190734A) is employed.
A focusing control based on the phase difference AF method is performed using an imaging element having a configuration in which pairs of phase difference detection pixels that receive one of a pair of beams passing through different parts of a pupil region of an imaging optical system and phase difference detection pixels that receive the other one of the pair of beams are discretely arranged on an imaging surface. In general, a correlation operation of detection signals is performed between the pairs of the phase difference detection pixels, a defocus amount is generated from a result of the correlation operation, and a focusing control is performed based on the defocus amount.
In JP2013-190734A, there is a problem that when an imaging element in which pairs of phase difference detection pixels are arranged at the same row is used, a focusing detection is not easily performed in a case where there is an edge that crosses a phase difference detection direction. Further, in order to solve the problem, JP2013-190734A discloses a technique for generating a defocus amount from results obtained by performing a correlation operation with respect to one of the pair of phase difference detection pixels and imaging pixels that receive both of the pair of beams in an upper adjacent row and in a lower adjacent row with reference to a row including the one of the pair of phase difference detection pixels, respectively, and performing a focusing control based on the defocus amount.